KANSAS CITY, Mo. (AP) -- Kansas City police have launched a criminal investigation into the death of professional wrestler Owen Hart.

Hart, 34, plummeted 70 feet to his death May 23 at Kemper Arena when the quick release on his harness opened early as he was being lowered into the ring.

"In looking at the rigging, I have a concern whether this was the safest way to do this stunt," said Police Maj. Gregory Mills.

Mills said detectives will investigate whether specialists hired by the World Wrestling Federation were using the appropriate equipment, whether they used it correctly and if Hart was properly trained to use it.

"We will be seeking expert advice to help us draw some conclusions," Mills said. "We can't say if it was right or wrong or if due caution was taken."

Three workers were on the arena catwalk with Hart before the stunt. Two were stagehands from the Kansas City area and the other was a rigger from Florida. All were hired by the WWF.

The rigger told police he connected a ring on Hart's vest to a snap hook, and connected the snap hook to a ring on the end of the rope. Then Hart stepped off the catwalk, putting his full weight onto the rope.

The rigger told police he saw Hart adjusting his vest and "Blue Blazer" costume as he dangled in midair, waiting for the cue to descend.

Then, the rigger said, he heard the distinctive "snap" that the quick release mechanism makes when it opens. That's when Hart plunged to the arena floor.

"He was not pushed, and the equipment that was to lower him to the floor does not appear to have been tampered with," Mills said. "We know someone else did not pull the ring to trigger the quick release."

Hart's family did not want to comment on the investigation, said family attorney Gary C. Robb.

WWF officials did not return telephone calls when an attempt was made to contact them about the investigation. The rigger who oversaw Hart's stunt could not be reached for comment.